1. Field of the Invention
The present invention generally relates to a method for determining location of an infrared-cut (IR-cut) filter film on a substrate.
2. Description of Related Art
With development of multimedia technology, image pick-up devices, such as digital cameras and video cameras are popular with customers. With current demand for miniaturization of such devices, quality of images produced by such devices is required to be high. The quality of such images is determined by quality of optical elements contained in the image pick-up devices.
Generally, an image pick-up device includes a lens module, and an image sensor, such as a charge coupled device (CCD) or a complementary metal oxide semiconductor device (CMOS). Responsive wavelengths of the CCD or CMOS ranges from 350 to 1500 nanometers and a wavelength of visible light ranges from 400 to 700 nanometers, infrared light, whose wavelength is longer than 700 nanometers, will cause image sensor errors, reducing quality of image produced by such an image sensor.
For this reason, an IR-cut filter is introduced into the lens module of the image pick-up device for filtering out the infrared light. The IR-cut filter includes a substrate and an IR-cut filter film on a surface of the substrate.
In process of assembling the lens modules, to maintain levels of optical consistency of each lens module, a location of the filter film on the substrate must be determined to make sure that a direction of orientation of the location of the filter film on the surface assembled in each lens module is identical.
What is needed, therefore, is a method for determining a location of the filter film on the substrate.